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What is a compound?

 A compound is a pure substance composed of two or more elements that are chemically combined.

Compounds can be written down using chemical formula which is a shorthand way used to represent them. For example the chemical formula of water is H2O. The compound water is composed of two elements, hydrogen and oxygen in the ratio of two to one.

Each compounds as its own set of distinct properties which identifies it from other pure substances. The compound glucose, chemical formula C6H12O6, is soluble in water aichnd produces a colorless solution which tastes sweet.

Compounds cannot be broken down into simpler substances by physical means. eg. distillation and filtration.

Compounds can broken down into their elements by thermal decomposition {heat}, electrolysis (electricity) and chemical reactions.

Mercuric oxide when heated decomposes into the elements mercury and oxygen. Water can be broken down into two parts hydrogen and one part oxygen by electrolysis. The element hydrogen can be produced by the chemical reaction of a metal with an acid.

A binary compound consists of two elements. Metals chemically combine with non-metals to produce compounds. The non-metal changes its suffix to an "ide" to indicate that a compound has been produced.

Binary compounds.

Metal element Non-metal element Compound
 Sodium  chlorine  sodium chloride
 Sodium  oxygen  sodium oxide
 Potassium  iodine  potassium iodide
 Magnesium  nitrogen  magnesium nitride
 Iron  sulfur or sulphur  iron sulfide or iron sulphide
 Lithium  hydrogen  lithium hydride
 Sodium  hydrogen  sodium hydride
 Calcium  bromine  calcium bromide
 Magnesium  oxygen  magnesium oxide
 Sodium  fluorine  sodium fluoride